Rhenium Diamino Dithiol Complexes. III. Lipophilic Ligands for Endotherapeutic Radiopharmaceuticals

Abstract

The chemistry and physical properties of a series of rhenium diamino dithiol (dadt) complexes are described. Liposolubility was enhanced by N-substitution of alkyl chains of C₁–C₁₄ length on one ligand structure, with longer chain lengths showing the higher solubility, but with a reduction of radiolabelling yield with ^99mTc and ¹⁸⁶Re. Among the Re^V=O [dadt] complexes synthesized, we found that 2,2,9,9-tetramethyl-4-N-alkyl-4,7-diaza-1,10-decanedithiol (alkyl = C₁–C₁₀) resulted in stable and lipiodol-soluble complexes. Biological characteristics of the C₆ ligand labelled with ^99mTc and ¹⁸⁶Re were compared, and indicated that the complexes behaved in a similar manner in rodents. The dadt ligands in combination with ¹⁸⁸Re or ¹⁸⁶Re and fatty acid oils merit further consideration as endotherapeutic radiopharmaceuticals for treatment of hepatoma and metastatic liver cancer.